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What is Biodiversity Net Gain?

Biodiversity Net Gain (BNG) is a new legal requirement affecting most types of planning applications in England. It came into force in February 2024.

The intention of the new legislation is to ensure the biodiversity value of development sites is measurably improved as a result of development. To achieve this, the law requires most planning applications to demonstrate a minimum 10% gain for biodiversity.

To which sites and developments does Biodiversity Net Gain apply?

The new BNG requirement has applied to major sites* since February 2024. Small sites** have been subject to BNG since the start of April 2024.

*For residential sites, this means sites that have an area of 0.5 ha or greater or where 10 or more homes are proposed. For non-residential sites, this means sites that have an area of 1 ha or greater or where additional floorspace of 1000 sqm or more is proposed.

**This means non-major sites.


The following sites and developments remain exempt:

  • Householder developments. These are developments that affect an existing house or its grounds, including domestic extensions, domestic outbuildings and domestic enclosures (fences, gates etc.)
  • Certain self-build and custom housebuilding applications. These are applications for new dwellings that are to be built by or on behalf of an individual (or collection of individuals) for occupation by that individual. The exemption only applies where:
    • The development consists of no more than 9 dwellings AND
    • The development site has an area of no more than 0.5 hectares AND
    • All dwellings in the application are of the self-build or custom build type.

There is also a de minimis exemption. This means development that meets both of the following two tests is exempt from the BNG requirement:

  1. The development does not impact an onsite priority habitat
  2. The development impacts:
    • Less than 25 square metres of onsite habitat that has a biodiversity value greater than zero
    • Less than 5 metres in length of onsite linear habitat.

In some local areas, Councils have adopted their own Biodiversity Net Gain planning policies that apply to sites and developments that would otherwise be exempt from the legal BNG requirement. If this is the case in your area, you will be expected to comply with the local BNG policy.

Definition of key terms
  • Priority habitat – these are specified habitats of principal importance to UK biodiversity. The list of priority habitats includes arable field margins, bogs, hedgerows, woodland, traditional orchards, heathland, reedbeds, meadows, rivers, ponds and more.
  • Biodiversity value – biodiversity value is measured using the government’s statutory biodiversity metric tool. The metric takes into account the size, condition, strategic significance and type of on-site habitats. If a site has a biodiversity value of zero that means it has no biodiversity value at all. This would likely apply, for example, to a site covered throughout by tarmac, concrete or traditional buildings
  • Linear habitat – hedgerow and watercourse habitats.

What do I need to do about Biodiversity Net Gain?

Exempt sites

If your development is exempt, you must include a statement explaining why it is exempt alongside your planning application.

Liable sites

If your development is liable for BNG, you are required by law to submit a Biodiversity Gain Plan before you commence development. You must not commence development until the plan is approved. The plan will demonstrate how the minimum 10% biodiversity gain will be achieved. The government has produced a Biodiversity Gain Plan template which is available online.

In addition, you must submit a biodiversity metric calculation alongside your planning application. This must be calculated using the government’s statutory biodiversity metric tool which is also available online. The metric assessment should be completed by a competent person. Although you do not necessarily need to share your Biodiversity Gain Plan with the council at this stage, you will likely require a draft version in order to complete the metric assessment.

Our advice is to submit your draft Biodiversity Gain Plan alongside your planning application as you may receive valuable feedback on its contents that will assist you to refine it. This will increase the chances of your finalised plan being approved the first time around.

Finally, you will need to submit a plan (drawing) that accurately shows the type and extent of all existing site habitats. This will require a site walkover.

How do I achieve a 10% gain for biodiversity?

Option 1 – onsite

The government’s expectation is that the full 10% gain will be delivered within the boundaries of the development site wherever possible. This will be achieved via the provision of new or enhanced green infrastructure. This includes things like woodlands, hedgerows, meadows, ponds and any other landscape features that provide wildlife habitats. You can extend or improve an existing habitat or create a whole new one.

New, onsite biodiversity features can include water bodies, woodlands and tree planting

The land owner will be legally responsible for both creating and maintaining the new habitat/s for a minimum period of 30 years.

If the 10% gain cannot be delivered onsite, there are two remaining options. However, you must be able to clearly justify why the net gain cannot be achieved onsite. If you are able to deliver less than the 10% gain onsite then you should do so and use the remaining options to make up the shortfall.

Option 2 – offsite

If you are unable to deliver the full 10% gain onsite, then the next best option is to deliver the gain offsite. This means creating new or enhanced habitats on land outside of the development site. This could be on adjacent land but the site can be anywhere in England. The biodiversity metric does look more favourably on offsite gains that are located close to the development site, however.

Biodiversity Net Gain
If you have a very large site, part of it could be developed and the rest given over to BNG

You can either make your own offsite gain on land in your ownership or you can buy offsite “units” from a land manager. There are already many companies in England offering these units for sale.

If you choose to deliver the gain on your own land, you will be legally responsible for maintaining the new habitat/s for a minimum period of 30 years. If you purchase your offsite units from a land manager, they will be legally responsible for maintaining the habitat/s over this period.

Option 3 – statutory biodiversity credits

Buying statutory credits is a last resort. It is only an option for developers who cannot achieve onsite or offsite biodiversity net gain. Developers who wish to buy statutory credits must explain why they cannot achieve the 10% gain using one or both of the preferred options outlined above.

Biodiversity credits
If you purchase credits, the biodiversity requirement will be met and managed by a third party

Developers can use a combination of the 3 options but must prioritise options 1 and 2, in order. If, for example, a developer is able to achieve a 5% onsite gain and a 3% offsite gain then they should only purchase statutory credits to make up the remaining 2%.

To purchase statutory credits, you must submit an application to Natural England. Natural England aims to consider your application within 8 weeks. Any credits you purchase will be non-refundable.

Follow the link below to find out more about the application process.

What Biodiversity Net Gain service does Planning Direct offer?

Planning Direct can assist you with all aspects of Biodiversity Net Gain. We are able to produce most BNG documents in-house. For larger and more complex developments, some BNG documents will be produced by one of our trusted ecology partners to ensure compliance with the legislation.

BNG only

We offer a standalone Biodiversity Net Gain service. This is suitable for site owners and developers who already have a handle on all other aspects of their planning application, e.g. planning drawings, written statements, reports and case management.

Comprehensive planning service

Planning Direct also offers a comprehensive planning application service at a competitive rate. If your application is liable for BNG, we will include it as standard. If you choose this service, we can ensure your BNG strategy is considered and incorporated from the earliest design stages. This will reduce the likelihood of delays or additional, unexpected costs further down the line.

In all cases, our BNG service includes:

  • Site survey
  • Completion of the statutory biodiversity metric calculation
  • Creation of a Biodiversity Gain Plan.

 How much control will I have?

There is no “one size fits all” approach to biodiversity and we can help you to work out which strategy is best for you. For example, if you’d like to incorporate biodiversity into the garden plan for your new home, we can assist you to select the best biodiversity features for each area, based on your unique vision, budget and maintenance capabilities. This approach will enable you to meet the biodiversity requirement whilst enhancing, at the same time, the amenity value and visual appeal of your garden.

On the other hand, if your primary goal is to keep costs down, we can assist you to design and deliver a cost-effective, robust and low maintenance biodiversity plan.

As with all our planning services, if you tell us your aims, we will tailor our approach to help you meet them!

If your development is affected by BNG, contact us today to find out how we can assist you. Our initial advice is always free of charge.

If you’d like to learn more about Biodiversity Net Gain, you can follow the link below to access an online copy of the government’s primary BNG guidance.

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